The present invention relates generally to a safety system for terminating the emission of a laser emission from a laser radiation source. More specifically, the present invention relates to a fail-safe laser shutter apparatus that electronically operates to terminate the supply power to a laser radiation source in a manner that renders the laser verifiably safe.
Continuous radiation type laser radiation sources have been employed in machine tools, medical machines such as laser scalpels and laser coagulators and length measuring machines. While lasers have become commonplace in these environments, lasers come with an inherent safety hazard. While the potential for burns are one risk related to laser operation, the larger concern is the ability of laser light to blind an unsuspecting individual. Surprisingly low intensity levels of laser radiation can cause permanent vision loss before the human eye can react. For this reason, vision safety should be of paramount importance in a laser environment.
Primarily, protection of vision from laser radiation exposure is accomplished through the use of safety goggles. Goggles with filters for blocking laser light at various wavelengths are available from a multitude of manufacturers. If chosen and worn properly, they provide adequate protection to those working with lasers while still allowing adequate visual perception to perform normal laboratory functions.
While safety goggles provide protection to announced visitors or those individuals who regularly work with lasers, the unexpected guest is still at extreme risk. To provide protection to these individuals, most lasers incorporate an interlock mechanism that shuts the laser down during an unexpected breach of the laser work area. Usually, a switch of some sort is connected to the cabinet doors of the work area that activates the interlock. However, most interlock mechanisms operate by shutting down the laser power supply. Doing this requires that the laser be restarted after each shutdown. This situation is very inconvenient, time consuming and may be damaging to the laser.
As an alternative to the interlock, many systems have instead incorporated a safety shutter. A safety shutter functions by physically blocking the laser beam when a breach in the laser work area occurs. It has typically been the practice to provide a mechanical shutter that is movable between open and closed positions for interrupting the laser output beam from a laser beam radiation source. In the event of failure of the mechanical shutter, however, the laser beam is emitted at an unexpected time, potentially putting a person at risk if injury. Such shutter systems are more convenient than the interlock mechanism, and they produce no strain on the laser system. The safety shutter can be controlled the same as an interlock and it provides a convenient means of stopping the laser beam when access to the operational system is required.
The difficulty that arises in mechanical shutters however results from the fact that the shutter needs to physically move into the path of the laser. With the all monolithic design of modern diode and fiber laser technology the implementation of a mechanical shutter would require free space optics to create a location for the shutter to physically block the beam. As a result, in many cases substantial loss in beam quality results from the inclusion of the needed free space optics.
There is therefore a need for a failsafe laser shutter mechanism that operates on monolithic laser systems without the need for cutting the main power or introducing free space optics. There is a further need for an electronic shutter that operates in a fail safe manner to reliably render a laser safe without requiring a full shutdown or the laser or substantial decrease in the laser beam quality.